Conventionally, there has been known a pump that moves a plunger in a first direction to pressurize fluid by a driving force applied to one end surface of the plunger in an axial direction. A seat receiver having a jaw shape is formed at the one end surface of the plunger to protrude radially outward of the plunger. A spring seat having a plate shape is attached to the plunger to engage with the seat receiver. The plunger is biased in a second direction opposite to the first direction by a biasing force of the spring through the spring seat.
A stopper is provided to prevent the plunger from falling from a cylinder hole when assembling the pump, or amounting the pump to an internal combustion engine.
Specifically, the plunger includes a large diameter portion and a small diameter portion. The large diameter portion is reciprocatably inserted into the cylinder hole and defines a pump chamber. The small diameter portion is positioned outside of the cylinder hole. A step surface is formed at a boundary region between the large diameter portion and the small diameter portion. The stopper has a cylindrical shape with a bottom, and a through hole is defined in the bottom for allowing the small diameter of the plunger to be inserted into the through hole. An engaging portion is formed around the through hole. The engaging portion engages with the step surface of the plunger.
The plunger is inserted into the cylinder hole and the stopper is fixed to the cylinder, and as a result, the step surface is engaged with the engaging portion, which prohibits the plunger from falling from the cylinder hole.
An outer diameter of the step surface needs to be greater than an inner diameter of the through hole. Therefore, the seat receiver and the small diameter portion are set to have diameters less than the through hole. After the seat receiver is inserted into the through hole, the small diameter portion is inserted into the through hole, and the plunger is moved until the step surface is brought into contact with the engaging portion.
A seat groove is formed at a boundary region of the seat receiver and the small diameter portion. The seat groove has a diameter less than the seat receiver. Then, the seat receiver is engaged with the seat groove by inserting the seat receiver into the seat groove (e.g., refer to Patent Literature 1: JP 2014-77361 A).
However, in the conventional pump, the diameter of the seat groove of the plunger is significantly less than the large diameter portion, and therefore the strength of the plunger may be decreased.
In view of the above, it is an objective of the present disclosure to provide a pump that includes a stopper to prevent a plunger from falling from a cylinder hole, where the strength of the plunger is increased.